This invention relates to aqueous dispersions of graft polymers or copolymers of ethylenically unsaturated perfluoroalkyl monomers containing aqueous polyurethane dispersions as the graft base, to a process for producing these dispersions by polymerizing or copolymerizing ethylenically unsaturated perfluoroalkyl monomers and, optionally, comonomers free from perfluoroalkyl groups in aqueous polyurethane dispersions as the graft base and to their use as hydrophobizing and oleophobizing agents for textiles.
2. Description of the Prior Art
Polymers containing perfluoroalkyl groups are suitable substances for hydrophobizing and oleophobizing (making oil or grease resistant) textiles or carpets. These polymers may be used in the form of aqueous emulsions. However, the production of aqueous emulsions by known methods of emulsion polymerization is difficult because ethylenically unsaturated perfluoroalkyl monomers are completely insoluble in water and stable emulsions cannot be obtained in water.
U.S. Pat. No. 3,403,122 describes an emulsion polymerization process for producing perfluoroalkyl polymers in aqueous media which contain from 5 to 50% of water-soluble, organic substances, for example acetone or methanol, to increase the solubility of the monomers in water. However, coarse, unstable dispersions are obtained in this way. In addition, water-soluble, organic solvents such as acetone or methanol are precipitants for numerous polymers so that this process cannot be applied to many of the copolymerization systems normally used.
U.S. Pat. No. 3,068,187 describes segmented copolymers, i.e. block or graft copolymers of ethylenically unsaturated perfluoroalkyl monomers with ethylenically unsaturated monomers containing less than 10% of fluorine and also a process for their production by emulsion polymerization in which the monomer containing less than 10% of fluorine, for example butadiene or chloroprene, is prepolymerized in aqueous emulsion, accompanied or followed by polymerization of the perfluoroalkyl monomer onto this pre-emulsion. However, the addition of water-soluble solvents (such as acetone or methanol) is necessary in this process, too, so that the stability of the emulsion obtained is reduced or, alternatively, complete coagulation may even occur.
To obviate these disadvantages, corresponding "perfluoroalkyl polymer emulsions" are generally prepared by solution polymerization in solvents which are insoluble in water (for example, methylisobutyl ketone, halogenated hydrocarbons or acetic acid esters) and are suitable as solvents both for the monomers and also for the polymers. By emulsifying this polymer solution in water using special emulsifying units or homogenizers, it is generally possible to obtain sufficiently fine, stable dispersions. However, this process is made complicated and expensive by the need for the additional step of emulsification, so that there is still a need for a technically simpler emulsion polymerization process.
It has now been found that hydrophobizing and oleophobizing dispersions which are stable in storage can be obtained by subjecting the ethylenically unsaturated perfluoroalkyl monomers described in detail hereinafter, preferably in combination with other vinyl monomers, to graft polymerization in the process of aqueous polyurethane dispersions. Irrespective of the graft yield, the total quantity of polymerized monomers is referred to as the "graft covering."
Although DE-OS No. 19 53 345, DE-OS No. 19 53 348 and DE-OS No. 9 53 349 describe the production of aqueous dispersions of polymers of ethylenically unsaturated monomers in aqueous polyurethane or oligourethane dispersions, the discovery according to the invention (that it is possible to produce storable dispersions of graft polymers or copolymers of ethylenically unsaturated perfluoroalkyl monomers) must be regarded as surprising, even in the light of the disclosure of the above-mentioned prior publications, because stable polymer emulsions can also be produced by other methods from the monomers mentioned in these prior publications, so that it could not have been expected that the above-mentioned difficulties involved in the production of aqueous dispersions of perfluoroalkyl polymers would be overcome by using aqueous polyurethane dispersions as the graft base. The dispersions according to the invention described in more detail hereinafter are further distinguished from the dispersions according to the above-mentioned prior publications by the fact that they are outstanding oleophobizing agents for textiles.